March 28, 1918] 



NATURE 



an the application of the ordinary ckansing methods. 

 Further experiments showed that the mites could be 

 carried by flies and moths. The common practice of 

 •dipping mite-attacked cheeses in hot water or steam- 

 ing them was found to be useless as a remedy. Fumi- 

 gation with sulphuretted hydrogen or sulphur dioxide 

 was also futile. Treatment with carbon bisulphide 

 proved very suco'^ssful, but treatment with formalin was 

 ineffective. In an experiment with carbon dioxide the 

 mites revived after a period of suspended anmiation 

 lasting for ninety-six hours. Methods of prevention of 

 mite attacks are indicated, and the article, which is 

 illustrated, also includes brief notes on the systematic 

 -ition, species, and life-history of the mites. 



I .REAT interest has been taken throughout the wide 

 uncle of his acquaintance in the experiment which 

 Prof. W. Somerville has been conducting during the 

 last seven years on his aptly named farm of ' Poverty 

 Bottom," with the object of demonstrating in actual 

 commercial farm practice the soundness of the view he 

 has so long and ably advocated, that the improve- 

 ment of English land offers in many parts of the 

 country an investment of a highly remunerative char- 

 acter. For his purpose a poor, thin soil on the chalk 

 seemed to be best suited as an object-lesson, in view of 

 the fact that the Cretaceous system is the most ex- 

 tensive single geological formation in England, and 

 hence results obtained in it would be capable of wide 

 application. In February, 1910, Prof. Somerville entered 

 into possession of "Poverty Bottom," a farm of 

 530 acres, situated on the South Downs near New- 

 haven, and at the time untenanted, unstocked, and 

 apparently all but barren. The outstandings measures 

 of improvement adopted were the liberal application of 

 basic slag, clearing off gorse, sowing of clovers, in- 

 cluding wild white clover, and fhe admixture of cattle 

 with sheep on the pastures. The use of basic slag 

 has effected a very striking improvement of the pas- 

 turage through the development of the leguminous 

 herbage, and the tillage land has shared in the im- 

 provement through the transference to it in the manure 

 of nitrogen collected in the meadows. Seven years' 

 farming has now been experienced, and the results 

 are summarised in a most interesting article by Prof. 

 Somerville in the current issue (February, 1918) of the 

 Journal of the Board of Agriculture. This article gives 

 many details of the system of improvement followed 

 which cannot be summarised here. It is estimated 

 that the head of stock has been increased by 50 per 

 cent., whilst, when the higher quality of the stock is 

 taken into account, the productivity of the farm in 

 terms of meat has been increased threefold in six 

 years. The net financial result in any year was very 

 largely a question of weather, but on the whole period, 

 after deducting losses, rent, etc., a credit balance of 

 more than 2200Z. remains. The average yearly re- 

 muneration of the farmer, it is estimated, would repre- 

 sent a sum of 338Z., together with a free house, as a 

 return for the investment of some 4000L of capital. 



A RECENT bulletin (No. 102, part i) of the Smith- 

 sonian Institution provides, under the title "The 

 Mineral Industries of the United States," a useful 

 popular account of coal and products from coal, which 

 may be read with advantage on both sides of the 

 Atlantic. The writer, Mr. Chester G. Gilbert, is cura- 

 tor of mineral technology in the U.S. National 

 Museum, and his object appears to be to urge the 

 importance of co-ordination and scientific control of 

 chemical industries. This lesson will have to be 

 learned in this country no less than in the United 

 States, but progress in this direction will depend very 

 much on the support given by public opinion. As, 

 however, few of the public know much about such 



NO. 2526, VOL. lOl] 



questions, anything which helps towards a popular 

 understanding of them is useful. This bulletin gives 

 within sixteen pages of print an outline of the origin 

 of coal, a comparison of the amount of coal deposits 

 in the several countries of the world, and an indication of 

 the methods used in the production of coke, gas, and 

 the other volatile products obtainable by the applica- 

 tion of heat. The illustrations added include a curious 

 diagiram of the products derived from coal and some 

 of their uses, which will serve to show to the un- 

 initiated the complex character of coal chemistry. 



When heat flows through the surface of a solid to 

 or from a gas in contact with the surface, it is well 

 known that the layer of stagnant gas close to the solid 

 interposes a considerable resistance to the flow. When 

 the object of the arrangement has been to get the maxi- 

 mum flow, it has been the custom to make the gas 

 flow rapidly over the surface of the solid. The ad- 

 vantage of this was pointed out by Osborne Reynolds 

 in 1874, and it has been verified experimentally by 

 Stanton in 1897, Nicolson in 1905, and more recently 

 by Jordan (Proc. Inst. Mech. Eng., 1909). Another 

 method of obtaining the same result is described by 

 Dr. C. Hering in a paper on "A New Principle in the 

 Flow of Heat," in the January number of the Journal 

 of the Franklin Institute. It is found that the resist- 

 ance of tne film of gas in contact with the solid may be 

 greatly reduced by increasing the temperature of the 

 surface of the solid. The flow through the bottom 

 of a kettle may, according to Dr. Hering, be in- 

 creased twenty-sevenfold by raising the temperature of 

 the metal surface in contact with the gas flame to 

 725° C. This can be done by interposing a thermal 

 resistance between the surface in contact with the 

 flame and that in contact with the water. It is pro- 

 posed to secure the same result in steam boilers by 

 attaching metallic lugs to the flame side of the flue, of 

 such length that their ends will be at about 725° C. 

 The results of a trial of the method on a practical 

 scale will be awaited with considerable interest. 



An interesting discussion on nitre-cake held by the 

 Nottingham Section of the Society of Chemical In- 

 dustr)- is reported in the Journal of the society for 

 December 15 last. According to Mr. G. C. Grisley, 

 the most successful method of utilising nitre-cake is 

 to substitute it for sulphuric acid in the manufacture 

 of hydrochloric acid and salt-cake from salt. It has 

 also been employed to obtain ferric sulphate for 

 sewage precipitation b> furnacing burnt pyrites with 

 nitre-cake, grinding, and leaching the product with 

 water. Further, it could be used as a diluent for 

 sulphuric acid in the manufacture of superphosphate. 

 Dr. Terlinck stated that he had used nitre-cake as a 

 substitute for sulphuric acid in the recovery of fats 

 from wool wash-waters, and he proposed to use it in 

 the purification of ammonium salts. The necessity for 

 workmen who handled nitre-cake being provided with 

 wooden clogs and india-rubber gloves was emphasised 

 by Mr. W. G. Timmans, who stated that in the 

 Nottingham district nitre-cake was used for lace 

 bleaching, grease extraction from wool, pickling 

 metals, and mineral-water manufacture. Dr. E. Naef 

 pointed out that the suggestions hitherto advanced 

 were based on the acidity of the nitre-cake, and that 

 the sodium sulphate remaining had still to be utilised. 

 One way of doing this was to reduce it to sodium 

 sulphide by grinding with anthracite, charcoal, or 

 boiler coal and heating at 5oo°-6oo° C, the yield 

 obtained being 95-98 per cent. Sulphur dioxide is 

 evolved if nitre-cake (rather than sodium sulpjhate) 

 is used, but this could be avoided by neutralising the 

 free acid with soda ash during the grinding. For the 

 production of sulphur dyes alone ';o,ooo tons of sodium 



